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litses
Participant

Join Date: Feb 2008
Posts: 3

Distance Protection for Earth Fault Detection

03/07/2008 8:25 AM

Hi everyone,

I would like some help in how to calculate / estimate the R1E resistance in isolated networks. As I found this resistance is the summation of the R1 resistance of the positive sequence plus the tower footing resistance plus the arc resistance plus a resistance if there is an infeed from the other side.

If I do not have sufficient data for these calculation, can I estimate this resistance as R1E=R1+10Ω?
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techno
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Canada - Member - Our strength is our diversity

Join Date: Jan 2007
Location: Canada
Posts: 1024
Good Answers: 40
#1

Re: Distance Protection for Earth Fault Detection

03/07/2008 2:15 PM

No. Safety can not be estimated.

The R1E resistance should be listed on your isolation transformer. If not, measure it like this http://www.transformerworld.co.uk/impedance.htm

The tower footing resistance depends on the materials, and thickness and can both be measured and calculated.

The arc resistance is a function of the air resistance, maximum humidity, and distance to the nearest earthed object which can also be measured and calculated.

CR4 Admin: removed broken link (Transformer World is all about the toys)

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